Peel the sweet potatoes, cut them into halves or quarters, then into thin slices. Put them up to cook, either in or over boiling water. Meanwhile, prepare the marinade. Combine the marinade ingredients in a medium-large bowl. AS soon as the sweet potatoes slices are tender, add them still hot, to the marinade. Mix gently. Steam the broccoli until bright green and just tender. Rinse under cold water and drain completely. Lay the broccoli carefully on top of the salad. Cover tightly and marinate for several hours. Within 15 minutes of serving, mix in the broccoli from the top. Serve garnished with thin slices of apple and toasted pecans.